VIN Question

[Tri-Poised]

I have a rather naive question on VIN numbers on a Road Runner vs. a Superbird in 1970. 

Since in 1970, a Plymouth Road Runner was either RM23 or RM21, and only came with a 383, 440 6bbl, or Hemi, would it not be true that any VIN number beginning with RM23U... would have to be a Superbird? Is that not the only way a RM23 car would have a U code, or 440 4 bbl?

Thanks.

[Aero426]

A GTX can also have the same VIN code.     So no, the U code by itself is not a determining factor.

[Tri-Poised]

Ah, yes. Good point!

[Hemi_tyme]

I have a rather naive question on VIN numbers on a Road Runner vs. a Superbird in 1970. 

Since in 1970, a Plymouth Road Runner was either RM23 or RM21, and only came with a 383, 440 6bbl, or Hemi, would it not be true that any VIN number beginning with RM23U... would have to be a Superbird? Is that not the only way a RM23 car would have a U code, or 440 4 bbl?

Thanks.

Yes
RM23U would be a Superbird only
RS23U would be a GTX

[hemi68charger]

Yes, a 70 GTX would have RS as the first two digits....... if you EVER see a RM with a U for engine, you have a Superbird, period....... now, an RM with a V or R for the engine code is another story........

[wyliemn71]

RM- road runner   RS- GTX

[Arnie Cunningham]

In 1970, yes, U code RM23 cars would have to be a Superbird.  (Unless the VIN was mistakenly stamped which did occasionally happen.)
The only other RM U code combinations I know of came in later years - couldn't you get a U code Road Runner in 1974 or so?  (about the same time the GTX became an option package on the Road Runner.)

[hemi68charger]

...- couldn't you get a U code Road Runner in 1974 or so?  (about the same time the GTX became an option package on the Road Runner.)

1972

[bannedbird]

I have seen (2) RM23U0 cars that were not Superbirds (no A13 code and J number not a Bird). I have at least one of the full VIN and tag info.  I have to dig them up... was 1980's pictures.
I was told a few days ago that a U code roadrunner recently sold and was documented.  Anyone have info on that car?

Please don't forget: They used to say Scary Larry's V code 72 roadrunner didn't exist ("they never made 6-packs in 1972").  And no "root beer" colored Superbirds.

[hemigeno]

Galen's Little White Book shows at least one known example of a RM23U0A 'Runner (i.e. non-Superbird;  Galen noted it had a 440-4/auto), and my edition was printed back in 2001.  That's the exception which proves the rule, I suppose.  

By now more examples than just that one may certainly have been unearthed... but generally-speaking, RM23U0 = Superbird

[Moparpoolman]

There could be a couple of GTXs out there that got mis-stamped RM instead of RS...

[moparstuart]

there was a thread on Forbbodiesonly that had a well documented  u code 70 Road Runner  ,  it looked legit